BR112013001238B1 - ELECTRODE, CATALYSTING DEVICE OF THE TYPE THAT ELECTRICALLY HEATS USING THE SAME, AND METHOD OF MANUFACTURING OF CATALYSTING DEVICE OF THE TYPE THAT ELECTRICALLY HEATS - Google Patents

Abstract

ELECTRODE, CATALYSTING DEVICE OF THE TYPE THAT ELECTRICALLY HEATS USING THE SAME, AND METHOD OF MANUFACTURING THE CATALYSTING DEVICE OF THE TYPE THAT ELECTRICALLY HEATS An electrode, according to an aspect of the present invention, is formed on a ceramic material. The electrodes include a matrix composed of a base composed of a ceramic material. The electrodes include an MCrAIY matrix (M being at least one material selected from FE, Co and Ni), and a dispersed phase that is dispersed in the matrix and composed of an oxide mineral having a laminated structure. The ratio of the area occupied by the dispersed phase in a cross section of the electrode is 40 to 80%. With the structure as shown, it becomes possible to suppress the increase in electrical resistance even after a thermal cycle has taken place.

Description

Technique field

The present invention relates to an electrode, a catalyst device of the type that is electrically heated using the electrode, and to a method of manufacturing a catalyst device of the type that is electrically heated

Fundamentals of technique

In recent times, EHC catalysts (electrically heated catalysts) receive important attention as an exhaust purification device that purifies the exhaust gases discharged from car engines or the like. In EHC catalysts, it is possible to forcibly activate a catalyst by means of electric heating even under conditions where the temperature of the exhaust gas is low and, therefore, the catalyst cannot be activated easily, such as, for example, , after ignition of the engine, and, therefore, increase the exhaust gas purification efficiency.

An EHC catalyst shown in Patent Literature 1 includes a cylindrical catalyst support having a honeycomb structure on which a catalyst, such as platinum and palladium, is supported, and a pair of electrodes that are electrically connected to the catalyst support and arranged in opposite positions to each other on the outer surface of the catalyst support. In this EHC catalyst, the catalyst supported on the catalyst support is activated by electrically heating the catalyst support between the pair of electrodes. In this way, toxic substances, such as unburned HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) in an exhaust gas that passes through the catalyst support, are removed via catalytic reaction.

Since an EHC catalyst is placed over an automobile discharge path or the like, the material for the electrode described above must have, in addition to electrical conductivity, heat resistance, acid resistance at a high temperature, re- 30 corrosion resistance in an exhaust gas atmosphere, or the like. Therefore, as mentioned in Patent Literature 1, a metallic material, such as a Ni-Cr alloy or an MCrAIY alloy (M being at least one material selected from Fe, Co and Ni), is used. In parallel, as for the material for the catalyst support described above, a ceramic material, such as SiC (silicon carbide), is used.

Once an EHC catalyst is placed on the discharge path, as described above, the electrode and catalyst support described above expand and contract repeatedly due to the thermal cycle (a normal temperature of about 900 ° C ). It should be noted that there is a problem, in the sense that cracking and / or peeling occurs in the electrode due to the difference between the coefficient of linear expansion of the metallic material that forms the electrode and the coefficient of the ceramic material that forms the support of catalyst. In order to solve this problem, in Patent Literature 2, the stress caused by the difference in linear expansion coefficients described above is relieved by inserting a porous intermediate layer made of a metallic material similar to the electrode between the electrode and the catalyst support.

List of citations Patent Literatures

Patent Literature 1: Publication of unexamined Japanese Patent Application No. 2011-106308.

Patent Literature 2: Publication of unexamined Japanese Patent Application No. 2011-132561.

Summary of the invention Technique Problem

The inventor found that the following problem must be solved.

The porous intermediate layer shown in Patent Literature 2 contains graphite and / or polyester. That is, it contains carbon. The inventor found that, when the intermediate layer contains carbon, the electrical resistance of the electrode increases significantly after a thermal cycle has taken place. It is assumed that this happens due to the Cr, which due to its acid resistance, reacts with the carbon in the intermediate layer and, thus, produces a Cr carbide, thus accelerating the electrode oxidation.

The present invention was built in view of the circumstances described above, and an object of the same is to provide an electrode capable of minimizing the increase in electrical resistance even after a thermal cycle has taken place.

Solution of the problem

An electrode according to a first aspect of the present invention is an electrode formed on a base material including a ceramic material, the electrode including: - a matrix that includes a Ni-Cr alloy (with a Cr content of 20 to 60 % by weight) or an MCrAIY alloy (M being at least one material selected from Fe, Co and Ni); and - a dispersed phase dispersed in the matrix, the dispersed phase including an oxide mineral with a laminated structure, being that - a ratio of area occupied by the dispersed phase in a cross section of the electrode is 40 to 80%.

With the structure as shown, it becomes possible to suppress the increase in electrical resistance even after a thermal cycle has taken place.

An electrode, according to a second aspect of the present invention, is the electrode described in the first aspect described above, in which the mineral oxide is at least one of bentonite and mica. With this aspect, the increase in electrical resistance is reliably eliminated, even after a thermal cycle has taken place.

An electrode, according to a third aspect of the present invention, is the electrode described in the first or second aspect described above, in which the electrode is formed by means of thermal spraying in a non-oxidizing atmosphere. With this aspect, the increase in electrical resistance is more reliably suppressed, even after a thermal cycle has taken place.

An electrode, according to a fourth aspect of the present invention, is the electrode described in any of the first to third aspects described above, in which the ceramic material includes SiC. A preferred ceramic material is SiC.

An electrically heated catalyst device according to a fifth aspect of the present invention includes: - a catalyst support comprising a ceramic material, on which a catalyst is supported; and - a pair of electrodes formed on the catalyst support, the electrode including: - a matrix comprising a Ni-Cr alloy (with a Cr content of 20 to 60% by weight) or an MCrAIY alloy (M at least one material selected from Fe, Co and Ni); and - a dispersed phase dispersed in the matrix, the dispersed phase including an oxide mineral having a laminated structure, and - an area ratio occupied by the dispersed phase in a cross section of the electrode is 40 to 80%.

With the structure as shown, it becomes possible to suppress the increase in electrical resistance even after a thermal cycle has taken place.

An electrically heated catalyst device according to a sixth aspect of the present invention is the electrically heated catalyst device described in the fifth aspect described above, in which the oxide material is at least one of bentonite and mica. With this aspect, the increase in electrical resistance is reliably suppressed, even after a thermal cycle has taken place.

An electrically heated catalyst device according to a seventh aspect of the present invention is the electrically heated catalyst device described in the fifth or sixth aspect described above, in which the electrode is formed by means of thermal spray in a non-oxidizing atmosphere. With this aspect, the increase in electrical resistance is more reliably suppressed, even after a thermal cycle has taken place.

An electrically heated catalyst device according to an eighth aspect of the present invention is the electrically heated catalyst device described in any one of the fifth to seventh aspects described above, in which the ceramic material includes SiC. Preferable ceramic material is SiC.

A method of making an electrically heated catalyst device in accordance with a ninth aspect of the present invention includes: - a step of producing a matrix particle including a Ni-Cr alloy (with a Cr content of 20 to 60% by weight) or an MCrAIY alloy (M being at least one material selected from Fe, Co and Ni); - a step of producing a dispersed phase particle including an oxide mineral having a laminated structure; - a step of forming a composite of the matrix particle and the dispersed phase particle and thereby producing a thermal spray particle; and - a step of thermally spraying the particle for thermal spraying on a catalyst support and, in this way, forming a pair of electrodes, the catalyst support including a ceramic material, on which a catalyst is supported, being - a reason The area occupied by the dispersed phase in a cross section of the electrode is 40 to 80%.

With the structure as shown, it becomes possible to suppress the increase in electrical resistance even after a thermal cycle has taken place.

One method of manufacturing an electrically heated catalyst device, according to a tenth aspect of the present invention, is the method of manufacturing an electrically heated catalyst device described in the ninth aspect described above, in which the mineral oxide is at least one among bentonite and mica. With such an aspect, the increase in electrical resistance is reliably eliminated, even after a thermal cycle has taken place.

A method of manufacturing an electrically heated catalyst device according to an eleventh aspect of the present invention is the method of manufacturing an electrically heated catalyst device described in the eleventh aspect described above, in which , in the step of producing a dispersed phase particle, the particle produced from the dispersed phase is sintered. It is preferable to sinter the dispersed phase particle composed of bentonite and / or mica in order to remove moisture from the particle.

One method of manufacturing an electrically heated catalyst device in accordance with an twelfth aspect of the present invention is the method of manufacturing an electrically heated catalyst device described in the eleventh aspect described above in which, in the stage of producing the thermal spray particle, the particle produced for thermal spray is sintered. It is preferable to sinter the dispersed phase particle composed of bentonite and / or mica in order to remove moisture from the particle.

A method of making an electrically heated catalyst device, in accordance with a thirteenth aspect of the present invention, is the method of making an electrically heated catalyst device described in any one of the ninth through the tenth according to aspects described above, in which, in the step of producing a matrix particle, an average particle diameter of the matrix particle is 10 to 50 pm. In this way, it is possible to effectively eliminate the oxidation of the matrix in the thermal spraying step.

A method of making an electrically heated catalyst device, according to a fourteenth aspect of the present invention, is the method of making an electrically heated catalyst device described in any one of the ninth through the tenth third aspects described above, in which the thermal spray particle is thermally sprayed in a non-oxidizing atmosphere. In this way, it is possible to effectively eliminate the oxidation of the matrix in the thermal spraying step.

One method of manufacturing an electrically heated catalyst device, in accordance with a fifteenth aspect of the present invention, is the method of manufacturing an electrically heated catalyst device described in the fourteenth aspect described above, in which the particle for thermal spraying is sprayed by plasma in the non-oxidizing atmosphere in which a flame is shielded by an Ar gas. In this way, it is possible to effectively eliminate the oxidation of the matrix in the thermal spraying step.

A method of manufacturing an electrically heated catalyst device, according to a sixteenth aspect of the present invention, is the method of manufacturing an electrically heated catalyst device described in the fourteenth aspect described above, in which the thermal spray particle is sprayed by plasma in the non-oxidizing atmosphere that is produced by reducing a pressure. In this way, it is possible to effectively eliminate the oxidation of the matrix in the thermal spraying step.

One method of making an electrically heated catalyst device, according to a seventeenth aspect of the present invention, is the method of making an electrically heated catalyst device described in the fourteenth aspect described above, in which the particle for thermal spraying is sprayed by flame in the non-oxidizing atmosphere, which turns out to be a reducing atmosphere produced by raising a ratio of acetylene gas to a gas mixed with oxygen and acetylene. In this way, it is possible to effectively eliminate the oxidation of the matrix in the thermal spraying step.

A method of making an electrically heated catalyst device, according to an eighteenth of the present invention, is the method of making an electrically heated catalyst device described in any one of the ninth to seventeenth aspects described above, in which the ceramic material includes SiC. A preferred ceramic material is SiC.

Advantageous effects of the invention

According to the present invention, it is possible to provide an electrode capable of minimizing the increase in electrical resistance even after a thermal cycle has taken place.

Brief description of the drawings

Figure 1 is a perspective view of an electric heating catalyst device 100 according to a first exemplary embodiment;

Figure 2 is a cross section in a part in which an anchoring layer 33 is formed;

Figure 3 is a graph showing a relationship between the area ratio of a dispersed phase, and the presence / absence of flaking and the electrical resistance of a sprayed thermal film;

Figure 4 is a photograph of a cross-sectional structure of a comparative example in which graphite is used as a dispersed phase;

Figure 5 is a photograph of a sprayed thermal film structure, according to a comparative example, taken after a thermal cycle has been carried out;

Figure 6 is an enlarged photograph of a sprayed thermal film structure, according to a comparative example, taken after a thermal cycle has been carried out;

Figure 7 is a photomicrograph of particles for thermal spraying that are used to form a thermal sprayed film, according to a first exemplary embodiment;

Figure 8 is a photomicrograph of particles for thermal spraying from a comparative example in which graphite is used as a dispersed phase;

Figure 9 is a cross-sectional photomicrograph of particles for thermal spraying of a comparative example;

Figure 10 is a photomicrograph of a matrix on a thermal sprayed film, according to a comparative example;

Figure 11 is a photograph of a structure in cross section of a thermal sprayed film, according to this exemplary modality;

Figure 12A is a photograph of a thermal sprayed film structure formed by atmospheric plasma spraying;

Figure 12B is a photograph of a structure of a thermal sprayed film formed by plasma spraying from Ar gas shielding.

Figure 12C is a photograph of a structure of a thermal sprayed film formed by means of reduced pressure plasma spraying;

Figure 13 is a photograph of a cross-sectional structure of a thermal sprayed film formed on a SiC catalyst support by means of thermal spraying of Ar gas shielding (before a thermal cycle is carried out);

Figure 14 is a photograph of a cross-sectional structure of a thermal sprayed film, shown in Figure 13, taken after a thermal cycle has taken place;

Figure 15 is a list of examples according to the present invention and comparative examples; and

Figure 16 is a photograph of a cross-sectional structure of a thermal sprayed film, according to Example 2.

Description of modalities

The specific exemplary embodiments to which the present invention applies are explained in detail below with reference to the drawings. However, the present invention is not limited to the exemplary embodiments shown below. In addition, for the sake of clarity and explanation, the following descriptions and drawings are simplified as appropriate.

First exemplary modality

First, an electric heating catalyst device according to this exemplary embodiment is explained with reference to Figures 1 and 2. Figure 1 is a perspective view of an electric heating catalyst device 100 according to a first exemplary embodiment. The electric heating catalytic device 100 is provided, for example, over an automobile discharge path or the like, and purifies an exhaust gas coming from the engine. As shown in Figure 1, the electrical heating catalyst device 100 includes a catalyst support 20 and electrodes 30.

The catalyst support 20 is a porous element on which a catalyst, such as platinum or palladium, is supported. In addition, since the catalyst support 20 alone is electrically heated, the catalyst support 20 is composed of a conductive ceramic material, for example, SiC (silicon carbide). As shown in Figure 1, the catalyst support 20 has an external cylindrical shape and has a honeycomb structure inside. As indicated by an arrow, an exhaust gas can flow through the catalyst support 20 in the axial direction of the catalyst support 20.

The electrodes 30 are a pair of electrodes that are used to feed an electrical current through the catalyst support 20 and thereby heat the catalyst support 20. The electrodes 30 are arranged in opposite directions to each other on the outer surface of the catalyst support 20. In addition, each electrode 30 extends from one end to the other end of the catalyst support 20 in the longitudinal direction. A terminal (not shown) is provided on each electrode 30 so that an electrical force can be supplied from a power source, such as a battery. It should be noted that one of the electrodes 30 serves as a positive pole, and the other electrode 30 serves as a negative pole. However, both electrodes 30 can serve as a positive or a negative pole. That is, there is no restriction on the direction of the current flowing through the catalyst support 20.

As shown in Figure 1, each electrode 30 includes a base layer 31, metal sheets 32 and clamping layers 33. In addition, Figure 2 is a cross section of a part in which a clamping layer 33 is formed.

As shown in Figure 1, the base layer 31 is a sprayed thermal film formed over the entire electrode formation area 30 on the outer surface of the catalyst support 20. That is, the base layers 31 are arranged in opposite directions from each other another on the outer surface of the catalyst support 20, and extending from one end to the other end of the catalyst support 20 in the longitudinal direction. As shown in Figure 2, the base layer 31 is physically in contact with the catalyst support 20 and electrically connected to the catalyst support 20.

As shown in Figure 2, the metal sheets 32 are arranged on the base layer 31, and are physically in contact with and electrically connected to the base layer 31. In addition, as shown in Figure 1, the metal sheets 32 extend into the circumferential direction over the entire formation area of the base layer 31. In addition, over each base layer 31, a plurality of metal sheets 32 are arranged at regular intervals along the axial direction of the catalyst support 20. In the example shown in Figure 1 , eight metal sheets 32 are arranged on each base layer 31. Of course, the number of metal sheets 32 is not limited to eight and can be arbitrarily determined. Each foil 32 is, for example, a thin sheet made of a metal, such as an Fe-Cr alloy.

The fixing layer 33 is a thermal sprayed film in the form of a button that is formed to cover the metallic sheet 32 in order to fix the metallic sheet 32 to the base layer 31. It should be noted that the fixing layer 33 is formed in the form of a button in order to relieve the tension that is caused by the difference between the linear expansion coefficient of the fixation layer 33 and the base layer 31, whose layers are thermal sprayed films based on metal, and the linear expansion coefficient of the catalyst support 20, which is made of a ceramic material. That is, by reducing the size of the fixing layer 33 as much as possible, the aforementioned tension is released. As shown in Figure 2, the attachment layers 33 are physically in contact with and electrically connected to the metal films 32 and the base layer 31. In addition, as shown in Figure 1, a plurality of attachment layers 33 is arranged at predetermined intervals on a metal sheet 32 in the longitudinal direction of the metal sheet 32 (in the axial direction of the catalyst support 20). In addition, the attachment layers 33 are arranged in such a way that the positions of the attachment layers 33 in the longitudinal direction of the metal sheets 32 are different between the mutually adjacent metal sheets 32.

With the structure described above, in the electric heating catalyst device 100, the catalyst support 20 is electrically heated between the pair of electrodes 30, and the catalyst supported on the catalyst support 20 is therefore activated. In this way, toxic substances, such as unburned HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide), in an exhaust gas that passes through catalyst support 20 are removed by the catalytic reaction.

In the electric heating catalyst device 100, according to this exemplary embodiment, the base layer 31 and the fixing layers 33, which are thermal sprayed films, have a characteristic aspect. In order to feed electricity to the metal sheets 32, the matrix, which is a thermal sprayed film, needs to be made of metal. Since the matrix needs to be robust enough for use at a high temperature, a preferable metal that is used to form the matrix, which is a thermal sprayed film, is a metal that has an excellent acid resistance at such a high temperature. as a Ni-Cr alloy (with a Cr content of 20 to 60% by weight) and an MCeAIY alloy (M being at least one material selected from Fe, Co and Ni). It should be noted that each of the Ni-Cr alloy and the MCrAIY alloy described above may contain other alloying elements.

In addition, the base layer 31 and the fixing layers 33, which are thermal sprayed films, include a dispersed phase in the metal matrix. The dispersed phase is used to reduce Young's modulus. It is preferable that the Young's modulus of the composite material made of the metal matrix and the dispersed phase is equal to or less than 50 GPa. For the thermal sprayed film, according to this exemplary modality, this dispersed phase has a laminated structure and is composed of an oxide mineral containing an oxide, such as SiO2 and AI2O3 as the main ingredients. In specific terms, the dispersed phase is preferably composed of bentonite, mica, or a mixture thereof.

A preferable ratio of the dispersed phase to the metal matrix is explained below with reference to Figure 3. Figure 3 is a graph showing a relationship between the area ratio of the dispersed phase, and the presence / absence of flaking and the electrical resistance. of the thermal sprayed film. It should be noted that the catalyst support is composed of SiC. The metal matrix is composed of Cr with 50% by weight of Ni. In addition, the dispersed phase is composed of bentonite. The horizontal geometric axis indicates the area ratio (%) of the dispersed phase. The vertical geometric axis on the left indicates the presence / absence of flaking of the sprayed thermal film. In addition, the vertical geometric axis on the right side indicates the electrical resistance of the sprayed thermal film. The electrical resistance is expressed on a logarithmic scale. In addition, in Figure 3, the data points for the presence / absence of flaking are plotted using an "x" mark (present flaking) and an "o" mark (missing flaking), and the marks are linked by a broken line. At the same time, the data points for the electrical resistance are plotted using an "Δ" mark, and the marks are connected by a solid line. The electrical resistance of the sprayed thermal film was measured at 10 mm measurement intervals using a tester. In addition, the area ratio of the phase dispersed in the cross-sectional structure of the sprayed thermal film (base layer 31 and fixation layer 33) can be easily obtained from a photograph of the structure in cross-section.

As shown in Figure 3, when the area ratio of the dispersed phase is less than 40%, the effect to relieve the stress is not sufficient. In this way, a flaking of the sprayed thermal film from the catalyst support was observed. On the other hand, when the area ratio of the dispersed phase is greater than 80%, the electrical resistance of the sprayed thermal film increases markedly. Based on this result, the area ratio of the dispersed phase is preferably 40 to 80%, and more preferably 50 to 70% as measured in the structure in cross section. A similar result was also obtained in a case in which the dispersed phase was mica.

The material that is used to form the dispersed phase must have a laminated structure in order to relieve the stress caused by the difference in linear expansion coefficient described above. In this regard, graphite, MoS2 (molybdenum disulfide), WS2 (tungsten disulfide), and h-BN (hexagonal boron nitride), all of which are known as a solid lubricant, can also be considered as candidates for the material used to form the dispersed phase, since they have a laminated structure.

A comparative example in which graphite is used as the dispersed phase is explained below with reference to Figure 4. Figure 4 is a photograph of a cross-sectional structure of a comparative example in which graphite is used as the dispersed phase. As explained above with reference to Figures 1 and 2, a base layer 31 having a thickness of 200 pm and a fixation layer 33 having a thickness of 400 pm were successively formed on a catalyst support 20 composed of SiC. a metallic sheet 32 is interspersed between the base layer 31 and the fixation layer 33. In the sprayed thermal film (the base layer 31 and the fixation layer 33) shown in Figure 4, the white area is the metal matrix composed of a Cr and Ni alloy at 50% by weight (hereinafter also referred to as "Ni-50Cr") and the black area is the dispersed phase composed of graphite. Figure 4 shows an initial state of thermal sprayed film before any thermal cycle is carried out and its electrical resistance was 0.1 Ω.

Figure 5 is a photograph of a structure of the pulverized film according to the comparative example, taken after the thermal cycles have been carried out. In specific terms, thermal cycles from an ambient temperature at 800 ° C were performed 2000 times. The electrical resistance of the sprayed thermal film had been increased significantly to around 500 Ω after the thermal cycles had taken place. As indicated by an arrow in Figure 5, a gray oxide was observed in the metal matrix. That is, the oxidation of the metal matrix had advanced.

Therefore, the inventor examined why the oxidation of the metal matrix had advanced. Figure 6 is an enlarged photograph of a structure of the pulverized film, according to the comparative example, taken after the thermal cycle has been carried out. As indicated by an arrow in Figure 6, a batch of gray Cr carbide pieces was observed in the white metal matrix (Ni-50Cr). When the carbonization of Cr advances in the metal matrix, as described above, the amount of Cr metal, which gives the acid resistance, decreases. As a result, the acid resistance becomes low. It is believed that, as a result of the lower acid resistance, the oxidation of the metal matrix had advanced. The probable period during which the Cr carbide is produced includes when particles for thermal spraying are produced, when thermal spraying is carried out, and when a thermal cycle is carried out. As described above, it has been found that the use of graphite as the dispersed phase is undesirable, since the graphite reacts with the metal matrix, in particular, with Cr at a high temperature.

Furthermore, it has been found that MoS2, WS2, and h-BN are decomposed and / or react with the metal matrix at a high temperature and, therefore, they are not an appropriate material to be used for the formation of the dispersed phase. For generalization purposes, since carbide-based, sulfide-based and nitride-based materials react with the metal matrix at a high temperature, they are not an appropriate material. In contrast, an oxide-based material composed of an oxide (SiO2 or AI2O3) that is more stable than Cr oxide at a high temperature does not react with the metal matrix even at a high temperature. Therefore, it is a preferable material. Specifically, a preferred material is a mineral that has a laminated structure and contains SiO2 or AI2O3 as the main ingredient, such as bentonite or mica.

In the following, a method of forming a thermal sprayed film will be explained.

First, matrix particles having a small specific surface, composed of a Ni-Cr alloy (with a Cr content of 20 to 60% by weight) or an MCrAIY alloy (M being at least one material selected from Fe, Co and Ni), which is used to form the metal matrix, are produced using a gas atomization method or the like. The average particle diameter of the matrix particles is preferably 10 to 50 pm, and more preferably 20 to 40 pm. In addition, it is preferable that the matrix particles do not contain fine particles whose diameter is less than 5 pm. In order to eliminate oxidation during the thermal spraying process, it is desirable that the particle diameter is large. On the other hand, in order to uniformly disperse the dispersed phase in the sprayed thermal film, it is desirable that the particle diameter is small.

In parallel, more or less spherical dispersed phase particles composed of bentonite or mica, which are used to form the dispersed phase, are produced using a spray drying method or the like. The average particle diameter of the dispersed phase particles is preferably 10 to 50 pm, and more preferably 20 to 40 pm. It should be noted that bentonite has such a property that it absorbs moisture and therefore swells, and mica contains crystalline water. In this way, these particles are sintered at a temperature of 1000 to 1000 ° C in a hydrogen atmosphere and the moisture contained in the dispersed phase particles is therefore removed.

Then, the matrix particles and the dispersed phase particles are formed into a composite by using a method of producing particle kneading at the same time using a polymer adhesive as a medium. After that, the composite particles are sintered again at a temperature of 1000 to 1100 ° C in a hydrogen atmosphere. As a result, particles for thermal spraying are produced. The average particle diameter of the particles for thermal spraying is preferably 30 to 150 µm.

Figure 7 is a photomicrograph of particles for thermal spraying that are used to form a thermal sprayed film according to the first exemplary embodiment. In this figure, the white particles are the matrix particles (Ni-50Cr), and the black particles are the dispersed phase particles (bentonite). The particle diameters of the matrix particles and those of the dispersed phase particles are both from 10 to 50 pm (mean particle diameter of 30 pm).

Then, the dispersed phase particles described above are sprayed by plasma onto the surface of a catalyst support 20 composed of SiC, and a base layer 31 having a thickness of 100 to 200 pm is thus formed.

Then, a metal sheet 32 having a thickness of 100 pm and a width of 1 mm is disposed on the base layer 31. A button-shaped attachment layer 33 having a thickness of 300 to 500 pm is formed on this metal sheet 32 by means of plasma spraying using a masking template.

Although plasma spraying can be performed in an atmospheric atmosphere, it is preferable for plasma spraying to be carried out in a non-oxidizing atmosphere. In specific terms, it is possible to eliminate oxidation during the thermal spraying process of a thermal sprayed film by performing plasma spraying with a plasma flame shield generated by an inert gas, such as Ar gas, and / or in an atmosphere of reduced pressure. In addition, instead of plasma spraying, flame spraying using an oxygen and acetylene combustion flame can be performed. Flame spraying can be done in a reducing atmosphere that is created by placing the combustion flame in a state rich in acetylene.

Next, the reason why particles for thermal spraying having a particle diameter of 30 to 150 pm are produced by forming a composite of matrix particles and dispersed phase particles as explained above with reference to Figure 7.

Figure 8 is a photomicrograph of particles for thermal spraying a comparative example in which graphite is used as the dispersed phase. Figure 9 is a cross-sectional photomicrograph of the particles for thermal spraying of the comparative example. As shown in Figure 9, the particles for the thermal spraying of the comparative example were produced by adhering the fine matrix particles (Ni-50Cr), which were crushed in flakes smaller than 5 pm in advance, on the surface of the particles graphite (coating). Fine matrix particles are produced by crushing the matrix particles produced by a fine particle gas atomization method.

It was found that when the matrix (Ni-50Cr) is crushed into a fine powder, as in the case of the comparative example shown in Figures 8 and 9, the oxidation of the Cr contained in the matrix advances before thermal cycles are carried out, ie , during the thermal spraying process. Figure 10 is a photomicrograph of a matrix on a thermal sprayed film according to the comparative example. As shown in Figure 10, a batch of Cr-type Cr oxide pieces was observed in the sprayed thermal film.

When the oxidation of Cr in the matrix advances during the thermal spraying process, as described above, the concentration of Cr in the matrix decreases relatively. That is, since the Cr concentration, which offers acid resistance, decreases in the matrix, the oxidation of the matrix tends to advance more easily during thermal cycles, thus causing a problem of the electrical resistance increasing. This is assumed to be caused since, as a result of spraying the matrix (Ni-50 Cr), the specific surface increases and oxidation is therefore accelerated during the thermal spraying process.

Therefore, according to this exemplary modality, as described above, matrix particles produced by means of a gas atomization method are used, since they are the particles for thermal spraying without crushing them in fine particles. In this way, it is possible not only to suppress matrix oxidation, but also to reduce the number of steps in the manufacturing process.

In addition, it has also been found that, when the matrix particles and the dispersed phase particles are simply mixed, the dispersed phase is not dispersed solely in the generated thermal sprayed film due to the difference in their specific gravities. Therefore, as explained above with reference to Figure 7, particles for thermal spraying are produced by forming a composite of matrix particles and dispersed phase particles. In this way, it is possible to disperse only the dispersed phase in the generated thermal spray film. Figure 11 is a photograph of a cross-sectional structure of a thermal film sprayed according to this exemplary modality. As shown in Figure 11, the dispersed phase (bentonite) is dispersed in a highly unique way in the matrix (Ni-50Cr) in the sprayed thermal film. It should be noted that the thermal sprayed film shown in Figure 11 was obtained by performing thermal spraying on a catalyst support composed of SiC in an atmospheric atmosphere.

Then, the results of the examination of the thermal spray atmospheres are explained with reference to Figures 12A to 12C. In order to prevent the oxidation of Cr in the matrix (Ni-50Cr) during the thermal spraying process, the inventors examined the gas shielded plasma spray and reduced pressure plasma spray at a pressure of 10 Pa. it should be noted that, for all thermal sprayed films, the dispersed phase is composed of bentonite and its area ratio is 60%. Figure 12 is a photograph of a thermal sprayed film structure that is formed by atmospheric plasma spraying. Figure 12B is a photograph of a structure of a thermal sprayed film formed by means of plasma spraying of gas shielded Ar. Figure 12B is a photograph of a structure of a thermal sprayed film formed by means of pressure plasma spraying. reduced.

As indicated by an arrow in Figure 12A, an oxide of Cr was observed in the thermal sprayed film obtained by atmospheric plasma spraying. In contrast, the amount of Cr oxide is less in the thermal sprayed films shown in Figures 12B and 12C than in the thermal sprayed film shown in Figure 12A. In addition, in the sprayed thermal film shown in Figure 12A, an increase in electrical resistance was observed after thermal cycles (100 to 900 ° C, 2000 cycles) were performed. In contrast, in the sprayed thermal films shown in Figures 12B and 12C, no increase in electrical resistance was observed even after the same thermal cycles were performed. In other words, it is believed that the oxidation of Cr during the thermal spraying process was suppressed and its acid resistance was sufficiently exerted. In addition, it has been found that the oxygen concentration in the thermal spray flame area needs to be equal to or less than 0.2% by volume in order to obtain a sufficient oxidation suppression effect.

Figure 13 is a photograph of a cross-sectional structure of a thermal sprayed film formed on a SiC catalyst support by means of thermal spraying of Ar gas shielding (before thermal cycles are carried out). The matrix is composed of Ni-50Cr, and the dispersed phase is composed of bentonite. Figure 14 is a photograph of a cross-sectional structure of a thermal spray film shown in Figure 13, taken after the thermal cycles (100 to 900 ° C, 2000 cycles) have been performed.

In addition, as an alternative method to thermal spraying of Ar gas shielding or to low pressure thermal spraying in plasma spraying, thermal spraying can be performed, in flame spraying using an oxygen and acetylene combustion flame, in a reduction atmosphere that is created by placing the combustion flame in a state rich in acetylene. In order to implement plasma spraying of Ar gas shielding or reduced pressure plasma spraying, it is necessary to make some changes to the atmospheric plasma spraying equipment. In contrast, the flame spraying described above has the advantage of requiring a small change.

In addition, in order to suppress matrix oxidation during the thermal spraying process, an active metal, such as Al, Ti and Mg, can be adhered to the matrix surface described above using the coating method or other methods. Since the active metal is preferably oxidized during the thermal spraying process, oxidation of the matrix can be suppressed.

Examples

Specific examples according to the present invention are explained below. However, the present invention is not limited to these examples. Figure 15 is a list of examples according to the present invention and comparative examples.

Example 1

The matrix particles having a particle diameter of 10 to 50 pm (average particle diameter of 30 pm), composed of a 50 wt% Cr and Ni alloy, which was used to form the metal matrix, were produced processor using a gas atomization method.

In parallel, dispersed phase particles having a particle diameter of 10 to 50 pm (mean particle diameter of 30 pm), composed of bentonite, which was used to form the dispersed phase, were produced using a drying method by spraying. These particles were sintered at a temperature of 1050 ° C in a hydrogen atmosphere.

Then, the matrix particles and the dispersed phase particles were formed into a composite using a kneading particle production method, at the same time using a polymer adhesive as a medium. In addition, the composite particles were sintered at a temperature of 1050 ° C in a hydrogen atmosphere. As a result, particles for thermal spraying were produced.

Then, the dispersed phase particles described above were sprayed by plasma onto the surface of a catalyst support 20 composed of SiC, and a base layer 31 having a thickness of 150 pm was therefore formed.

Then, a metal sheet 32 having a thickness of 100 pm and a width of 1 mm was disposed over the base layer 31. In addition, a fixing layer 33 having a thickness of 400 pm was formed on the metal sheet 32 by means of plasma spraying using a masking template.

A Metco F4 pistol was used as a plasma spray device. As for the plasma gas, a gas mixed with Ar and H2 gas was used, it was composed of an Ar gas with a flow rate of 60 L / min and an H2 gas with a flow rate of 10 L / min. The plasma current was 600 A. The plasma voltage was 60 V. The thermal spray distance was 150 mm. In addition, the particle supply rate for thermal spraying was 30 g / min. In addition, in order to suppress the oxidation of the matrix during the thermal spraying process, the plasma flame was shielded with an Ar gas.

For the sprayed thermal film (the base layer 31 and the fixation layer 33) according to Example 1, the area ratio of the dispersed phase was adjusted to 40%. After the thermal cycles (100 to 900 ° C, 2000 cycles) had been carried out, the electrical resistance was measured at 10 mm measurement intervals using a tester. As a result, the measured electrical resistance was 3.0 Ω and presented an excellent result.

Example 2

A sprayed thermal film was formed in the same way as Example 1, with the exception that the area ratio of the dispersed phase is adjusted to 60%. As a result, the electrical resistance measured after the thermal cycles was 2.8 Ω and presented an excellent result. Figure 16 is a photograph of a cross-sectional structure of a thermal sprayed film according to Example 2.

Example 3

A sprayed thermal film was formed in the same manner as Example 1, with the exception that the area ratio of the dispersed phase is adjusted to 80%. As a result, the electrical resistance measured after the thermal cycles was 4.0 Ω and showed an excellent result, although it was slightly higher than in Examples 1 and 2.

Example 4

A thermal sprayed film was formed in the same manner as Example 2, with the exception that mica was used as the material used to form the dispersed phase. As a result, the electrical resistance measured after the thermal cycles was 3.1 Ω and presented an excellent result.

Example 5

A sprayed thermal film was formed in the same way as Example 2, with the exception of a 25% by weight Co alloy, 16% by weight NI, 6.5% by weight Cr, 0.5% Al % by weight and Y have been used as the material used to form the matrix. As a result, the electrical resistance measured after the thermal cycles was 3.5 Ω and presented an excellent result.

Example 6

A sprayed thermal film was formed in the same manner as Example 2, with the exception of mica being used as the material used to form the dispersed phase. As a result, the electrical resistance measured after the thermal cycles was 3.6 Ω and presented an excellent result.

Example 7

A sprayed thermal film was formed in the same manner as Example 2, with the exception of a 23% by weight Ni alloy, 20% by weight Co, 8.5% by weight Cr, 0.6% Al % by weight and Y have been used as the material used to form the matrix. As a result, the electrical resistance measured after the thermal cycles was 3.5 Ω and presented an excellent result.

Example 8

A sprayed thermal film was formed in the same manner as Example 2, with the exception of a 20% by weight Fe alloy, 6.5% by weight Cr, 0.5% by weight Al, and Y ter been used as the material used to form the matrix. As a result, the electrical resistance measured after the thermal cycles was 3.3 Ω and presented an excellent result.

Example 9

A thermal sprayed film was formed in the same manner as Example 1, with the exception that atmospheric plasma spraying was carried out without shielding the plasma flame with an Ar gas. As a result, the electrical resistance measured after the thermal cycles was 20 Ω.

Example 10

A thermal sprayed film was formed in the same manner as in Example 2, with the exception that atmospheric plasma spraying was carried out without shielding the plasma flame with an Ar gas, and the particle diameter of the matrix particles, which were used to produce the particles for thermal spraying, it was less than 5 pm. As a result, the electrical resistance measured after the thermal cycles was 46 Ω.

Comparative Example 1

A thermal sprayed film was formed in the same manner as Example 2, with the exception that graphite was used as the material used to form the dispersed phase. As a result, the electrical resistance measured after the thermal cycles was 490 Ω and was extremely high. It is believed that, as explained above with reference to Figure 6, since graphite was used as the material used to form the dispersed phase, it could not produce an excellent result.

Comparative Example 2

A thermal sprayed film was formed in the same manner as Example 2, with the exception that atmospheric plasma spraying was carried out without shielding the plasma flame by means of an Ar gas and that graphite was used as the material used for form the dispersed phase. As a result, the electrical resistance measured after the thermal cycles was 310 Ω and was extremely high. It is believed that, as explained above with reference to Figure 6, since graphite was used as the material used to form the dispersed phase, it could not produce an excellent result.

Comparative Example 3

A thermal sprayed film was formed in the same manner as Example 2, with the exception that graphite was used as the material used to form the dispersed phase. As a result, the electrical resistance measured after the thermal cycles was 200 Ω and was of a high value. It is believed that, as explained above with reference to Figure 6, since graphite was used as the material used to form the dispersed phase, it could not produce an excellent result.

Comparative Example 4

A thermal spray film was formed in the same manner as Example 9, with the exception that the area ratio of the dispersed phase was adjusted to 30%. As a result, the sprayed thermal film was peeled off the catalyst support 20 and, thus, the measured electrical resistance could not be measured. It is believed that the area ratio of the dispersed phase was so small that it could not produce an excellent result.

Comparative Example 5

A sprayed thermal film was formed in the same manner as Example 1, with the exception that the area ratio of the dispersed phase was adjusted to 30%. As a result, the sprayed thermal film was peeled off the catalyst support 20 and, thus, the measured electrical resistance could not be measured. It is believed that the area ratio of the dispersed phase was so small that it could not produce an excellent result.

As can be seen from the results of Examples 1 to 10, thermal sprayed films having an electrical resistance equal to or less than 50 Ω, as measured after the thermal cycles, were obtained by adjusting the content of the dispersed phase composed of bentonite or 40 to 80% mica, as indicated in the area ratio. In addition, as can be seen from the results of Examples 1 to 8, extremely excellent thermal sprayed films having an electrical resistance equal to or less than 5 Ω, as measured after thermal cycles, were obtained by performing the spraying thermal in a non-oxidizing atmosphere. In addition, as for the matrix particles used for the production of the thermal spray particles, the suppression of oxidation during the thermal spray process became more effective and more excellent results were obtained when the average particle diameter was around 30 pm than when the matrix particles were crushed into a fine powder having an average particle diameter less than 5 pm.

It should be noted that the present invention is not limited to the exemplary modalities described above, and that various modifications can be made to the exemplary modalities without departing from the spirit of the present invention.

List of Reference Signs 20 - Catalyst support 30 - Electrode 31 - Base layer 32 - Metal foil 33 - Fixing layer 100 - Electric heating catalyst device

Claims (18)

1. Electrode for an electrically heated catalyst device, formed on a base material comprising a ceramic material, the electrode being CHARACTERIZED by the fact that it comprises: - a matrix comprising a Ni-Cr alloy with a content of Cr of 20 to 60% by weight, or an MCrAIY alloy, M being at least one material selected from Fe, Co and Ni; and - a dispersed phase dispersed in the matrix, the dispersed phase comprising an oxide mineral having a laminated structure, being that - an area ratio occupied by the dispersed phase in a cross section of the electrode is 40 to 80%. 2. Electrode for a catalytic device of the type that is electrically heated, according to claim 1, CHARACTERIZED by the fact that the mineral oxide is at least one among bentonite and mica. 3. Electrode for a catalytic device of the type that is electrically heated, according to claim 1 or 2, CHARACTERIZED by the fact that the electrode is formed by means of thermal spray in a non-oxidizing atmosphere. 4. Electrode for an electrically heated catalyst device according to any one of claims 1 to 3, CHARACTERIZED by the fact that the ceramic material contains SiC. 5. Catalytic device of the type that is electrically heated, CHARACTERIZED by the fact that it comprises: - a catalyst support comprising a ceramic material, on which a catalyst is supported; and - a pair of electrodes formed on the catalyst support, the electrode comprising: - a matrix comprising a Ni-Cr alloy with a Cr content of 20 to 60% by weight, or an MCrAIY, M alloy being at least one material selected from Fe, Co and Ni; and - a dispersed phase dispersed in the matrix, the dispersed phase comprising an oxide mineral having a laminated structure, and - an area ratio occupied by the dispersed phase in a cross section of the electrode is 40 to 80%. 6. Catalytic device of the type that is electrically heated, according to claim 5, CHARACTERIZED by the fact that the oxide material is at least one among bentonite and mica. 7. Catalytic device of the type that is electrically heated, according to claim 5 or 6, CHARACTERIZED by the fact that the electrode is formed by means of thermal spraying in a non-oxidizing atmosphere. 8. Catalytic device of the electrically heated type according to any one of claims 5 to 7, CHARACTERIZED by the fact that the ceramic material contains SiC. 9. Method of manufacturing an electrically heated catalyst device, the method being CHARACTERIZED by the fact that it comprises: - a step of producing a matrix particle comprising a Ni-Cr alloy with a Cr content of 20 to 60% by weight, or an MCrAIY, M alloy being at least one material selected from Fe, Co and Ni; - a step of producing a dispersed phase particle comprising an oxide mineral having a laminated structure; - a step of forming a composite of the matrix particle and the dispersed phase particle and thereby producing a thermal spray particle; and - a step of thermally spraying the particle for thermal spraying on a catalyst support and, in this way, forming a pair of electrodes, the catalyst support comprising a ceramic material, on which a catalyst is supported, being - a reason The area occupied by the dispersed phase in a cross section of the electrode is 40 to 80%. 10. Method of manufacture of a catalytic device of the type that is electrically heated, according to claim 9, CHARACTERIZED by the fact that the mineral oxide is at least one among bentonite and mica. 11. Method of manufacturing an electrically heated catalyst device according to claim 10, CHARACTERIZED by the fact that, in the step of producing a particle of a dispersed phase, the particle produced from the dispersed phase is sintered. 12. Method of manufacturing an electrically heated catalyst device according to claim 11, CHARACTERIZED by the fact that, in the step of producing a thermal spray particle, the particle produced for thermal spray is sintered. 13. Method of manufacturing an electrically heated catalyst device according to any one of claims 9 to 12, CHARACTERIZED by the fact that, in the step of producing a particle of a matrix, an average particle diameter of the particle of the matrix is from 10 to 50 pm. 14. Method of manufacturing an electrically heated catalyst device according to any one of claims 9 to 13, CHARACTERIZED by the fact that, in the step of forming an electrode, the particle for thermal spraying is thermally sprayed in a non-oxidizing atmosphere. 15. Method of manufacturing an electrically heated catalyst device according to claim 14, CHARACTERIZED by the fact that the thermal spray particle is sprayed by plasma in the non-oxidizing atmosphere in which a flame is shielded by a gas Air. 16. Method of manufacturing an electrically heated catalyst device according to claim 14, CHARACTERIZED by the fact that the thermal spray particle is sprayed by plasma in the non-oxidizing atmosphere that is produced by reducing a pressure. 17. Method of manufacturing an electrically heated catalyst device according to claim 14, CHARACTERIZED by the fact that the thermal spray particle is sprayed by flame in the non-oxidizing atmosphere, which becomes a reducing atmosphere produced by raising a ratio of acetylene gas to a gas mixed with oxygen and acetylene. 18. Method of manufacturing an electrically heated catalyst device according to any one of claims 9 to 17, CHARACTERIZED by the fact that the ceramic material contains SiC.

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